CN108842805B - Pile-supported reinforced embankment pile soil stress determination method - Google Patents
Pile-supported reinforced embankment pile soil stress determination method Download PDFInfo
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D27/00—Foundations as substructures
- E02D27/10—Deep foundations
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- E—FIXED CONSTRUCTIONS
- E01—CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
- E01C—CONSTRUCTION OF, OR SURFACES FOR, ROADS, SPORTS GROUNDS, OR THE LIKE; MACHINES OR AUXILIARY TOOLS FOR CONSTRUCTION OR REPAIR
- E01C3/00—Foundations for pavings
- E01C3/04—Foundations produced by soil stabilisation
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
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Abstract
The invention discloses a method for determining pile soil stress of a pile-supported reinforced embankment, which comprises the following steps: (10) acquiring parameters: acquiring physical parameters of the pile-supported reinforced embankment, including pile length, pile distance, pile cap size, embankment filling height, the position of a reinforced body grid, external loading of the top surface of the embankment and the like; (20) and (3) calculating the additional pressure of the pile top: calculating pile top additional pressure according to the setting position of the reinforcement body based on the instability destruction mode of the reinforced embankment; (30) and (3) calculating the pile top distributed load: calculating the pile top distributed load according to the pile top additional pressure and the pile top distributed load in the reinforcement-free embankment; (40) calculating the soil reaction force between piles: and calculating the soil reaction force between piles according to the total load of the embankment and the load distributed on the pile top. The pile-supported reinforced embankment pile soil stress determination method is based on an embankment failure mode, and meanwhile, the reinforcement body setting mode is considered, so that the result is more accurate.
Description
Technical Field
The invention belongs to the technical field of road engineering, and particularly relates to a pile-supported reinforced embankment pile soil stress determination method based on an embankment failure mode and considering a reinforced body setting mode, wherein the result is more accurate.
Background
The pile-supported reinforced embankment is generally composed of soil, piles, horizontal reinforcement bodies, pile caps, embankment filling soil and the like. When the pile-supported reinforced embankment is adopted, part of embankment load is directly transmitted to the pile through the soil arch effect and is transmitted to the hard lower lying layer through the pile; the other part of the load is transmitted to the pile top through the geosynthetic material (namely, the horizontal reinforced body) and is transmitted to the hard subjacent layer through the pile.
The simplified calculation method of the pile-supported reinforced embankment at present mainly separates the soil arch effect and the film drawing effect of a reinforced body and takes the soil arch effect and the film drawing effect into independent consideration, and adopts two steps for analysis: firstly, applying a soil arching effect theory based on different failure modes, and giving pressure acting on the top surface of a reinforcement body; and secondly, determining the tension of the reinforced material by applying a film drawing theory according to the pressure of the top surface of the reinforced body. The method only considers the influence of the bearing capacity of the foundation and the rigidity influence of the reinforced material in the calculation of the pulling force, can not simultaneously meet the vertical balance condition in the filling of the embankment and the deformation compatibility condition of the reinforced material, and can not consider the interaction property of the reinforced soil interface and the influence of the interaction property on the properties of the pile-supported reinforced embankment. Therefore, the calculation results of different simplified methods are greatly different, for example, under the condition of the given maximum strain, the calculation result of the reinforcement tension of British standard BS8006 is about 2 times larger than that of Japanese detailed rules, and is about 5 times larger than that of the northern Europe manual.
Therefore, the prior art has the problems that: the calculation result error of the pile-supported reinforced embankment pile soil stress is large because the setting effect of the reinforcement body and the combined action of the reinforcement and the soil are not considered.
Disclosure of Invention
The invention aims to provide a pile-supported reinforced embankment pile soil stress determination method, which is based on an embankment failure mode and considers a reinforcement body setting mode, so that the result is more accurate.
The technical solution for realizing the purpose of the invention is as follows:
a pile-supported reinforced embankment pile soil stress determination method is characterized by comprising the following steps:
(10) acquiring parameters: acquiring physical parameters of the pile-supported reinforced embankment, including pile length, pile distance, pile cap size, embankment filling height, the position of a reinforced body grid and external loading of the top surface of the embankment;
(20) and (3) calculating the additional pressure of the pile top: calculating pile top additional pressure according to the setting position of the reinforcement body based on the instability destruction mode of the reinforced embankment;
(30) and (3) calculating the pile top distributed load: calculating the pile top distributed load according to the pile top additional pressure and the pile top distributed load in the reinforcement-free embankment;
(40) calculating the soil reaction force between piles: and calculating the soil reaction force between piles according to the total load of the embankment and the load distributed on the pile top.
Compared with the prior art, the invention has the following remarkable advantages:
according to the pile-bearing type reinforced embankment pile-soil stress determination method, the influence of the arrangement position and rigidity of the reinforced body and the interaction of the reinforcement and the soil are considered, and derivation is carried out based on the actual sliding surface of the pile-bearing type reinforced embankment, so that the method is closer to the actual situation, the error is reduced, the calculation method is simple and convenient, and the method is easy to popularize and apply in actual engineering.
The invention is described in further detail below with reference to the figures and the detailed description.
Drawings
Fig. 1 is a main flow chart of the pile-bearing reinforced embankment pile soil stress determination method of the present invention.
Fig. 2 is a deformed cloud picture of the reinforced embankment. Wherein, fig. 2a shows that the reinforcement body is arranged at a certain distance u above the pile top, and fig. 2b shows that the reinforcement body is arranged at the pile top.
Fig. 3 is a schematic view of the reinforcement body arranged at the position u above the pile top.
Fig. 4 is a schematic view of the reinforcement body arranged at the pile top.
Fig. 5 is a deformation diagram of the reinforcing body with smaller rigidity arranged at the position u above the pile top.
FIG. 6 is a schematic diagram of the static analysis of the earth wedge OO' A.
Detailed Description
As shown in fig. 1, the method for determining pile soil stress of the pile-supported reinforced embankment of the present invention includes the following steps:
(10) acquiring parameters: acquiring physical parameters of the pile-supported reinforced embankment, including pile length, pile distance, pile cap size, embankment filling height, the position of a reinforced body grid, external loading of the top surface of the embankment and the like;
(20) and (3) calculating the additional pressure of the pile top: calculating pile top additional pressure according to the setting position of the reinforcement body based on the instability destruction mode of the reinforced embankment;
the instability failure mode of the reinforced embankment is that a whole analysis model of each element (filling-reinforced body-pile-embankment) of the pile-supported reinforced embankment is established through PFC (power factor correction) numerical analysis, wherein the reinforced body is generated by adopting parallel bonding model circular particles, and the microscopical parameters of the reinforced body are obtained by repeatedly fitting a tension-deformation curve of the reinforced body (usually geogrid) obtained through a tensile test in a trial calculation mode.
Loading on the surface of the pile-supported reinforced embankment, circulating to the balance requirement, and recording parameters such as corresponding displacement and stress under each load.
The "deformed cloud" is drawn by FISH language in PFC, as shown in fig. 2. Different colors are set for the deformation size, so that the displacement change and distribution in the soil are distinguished. And describing according to the stress change and displacement distribution of the embankment to obtain a destabilization sliding mode of the reinforced embankment and obtain a system sliding surface forming and developing mode under the combined action of filling, reinforcing bodies, piles and the embankment. It can be known from numerical calculation and experimental analysis that the setting positions of the reinforcement bodies are different, the sliding instability mode is changed, when the reinforcement bodies are arranged, the damage surfaces are blocked by the reinforcement materials, the relative displacement of the soil body is reduced, and therefore the embankment sliding surface is limited within the range of the embankment reasonably by changing the setting positions and the rigidity of the reinforcement bodies (as shown in figure 2).
The arrangement position of the reinforcing body takes the following two conditions into consideration: the reinforcement bodies are respectively arranged at the position u above the pile top as shown in fig. 3, and the reinforcement bodies are arranged at the pile top as shown in fig. 4.
And setting the sliding failure surface to be OABC or OAB 'C', considering the influence of the arrangement position and rigidity of the reinforcement body, and deducing a calculation formula of pile top additional pressure on the basis of a failure mode.
The (20) pile top additional pressure calculating step comprises:
(21) when the reinforcement body is arranged above the pile top by a certain distance u, the rigidity of the reinforcement body is higher, and the tensile modulus is more than 50GPa,
additional pressure of one layer of grid pile top:
adding pressure to the tops of two or more layers of n grid piles:
when the rigidity of the reinforced body is larger, the triangular soil wedge OO' A is taken as an investigation object, and the distribution load delta p of the pile top increased under the action of the tensile force of the reinforced body is deducedt。
(22) When the reinforcement body is arranged above the pile top by a certain distance u, the rigidity of the reinforcement body is smaller, and the tensile modulus is not more than 50GPa,
the additional pressure of the pile top of the layer of reinforcement body is as follows:
two-layer and more than two-layer n add pressure to the top of the reinforced body pile:
wherein: t is the tension of the reinforcement body, and u is the vertical distance between the grating and the pile top;
the internal friction angle of the soil body; a is the cross section area of the pile cap, and for a square pile cap, A is a2And a is the width of the cross section of the pile cap, and the pile cap is circular
a is the diameter of the pile cap, α is the included angle between the fracture surface and the horizontal plane, namely the included angle between the OA or O' A side and the horizontal plane,
when the base bottom surface is completely rough, α is
When the bottom surface of the foundation is completely smooth, the included angle is
h is the embankment filling height, and i is the number of layers of the grids.
When the rigidity of the reinforcement is lower, the reinforcement deforms along O 'A and OA under the action of ultimate load, as shown in figure 5, and the additional load delta p of the pile top under the bar load caused by the reinforcement is deduced by the static balance of the soil wedge OO' A (as shown in figure 6)t。
(23) When the reinforcement body is arranged at the pile top, the rigidity of the reinforcement body is higher, and the tensile modulus of the reinforcement body is greater than 50GPa, the pile top is subjected to additional pressure:
when the rigidity of the reinforcement body is higher, the vertical deformation of the grating is small under the action of load
(24) When the reinforcement body is arranged at the pile top, the rigidity of the reinforcement body is smaller, and the tensile modulus of the reinforcement body is not more than 50GPa, the pile top is subjected to additional pressure:
wherein: delta is the friction angle between the reinforcement body and the soil body, and the average value of delta is taken
When the rigidity of the reinforcement body is lower, the static balance of the earth wedge OO' A deduces the distribution load delta p of the pile top increased under the tensile force action of the reinforcement bodyt。
(30) And (3) calculating the pile top distributed load: calculating the pile top distributed load according to the pile top additional pressure and the pile top distributed load in the reinforcement-free embankment;
and (30) the step of calculating the pile top distributed load is specifically to calculate the pile top distributed load according to the following formula:
pgeneral assembly＝p+Δpt。
Wherein: and p is the pile top distributed load in the non-reinforced embankment and is obtained according to a correlation formula of the soil arch effect. Δ ptAdditional pressure is applied to the pile top, obtained from the previous process.
The above formula is to consider the embankment destruction modeUnder the action of additional tension of reinforcement body in formula and soil, load p is distributed on pile top under the action of loadGeneral assemblyA simplified formula of (c).
(40) Calculating the soil reaction force between piles: and calculating the soil reaction force between piles according to the total load of the embankment and the load distributed on the pile top.
And (40) calculating the soil reaction force among the piles specifically comprises the following steps of calculating the soil reaction force among the piles according to the following formula:
wherein: sigma'sThe reaction force of soil between piles is shown, gamma is the weighted gravity of the filled soil of the embankment, h is the filled soil height of the embankment, s is the distance between piles, and q is the external load of the top surface of the embankment.
The invention adopts the step of calculating the additional pressure of the pile top according to the setting position of the reinforcement body based on the instability failure mode of the reinforced embankment, and deduces and obtains a simplified calculation method of the pile top stress by considering the failure mode of the embankment and the influence of the rigidity of the reinforcement body, so that the pile top stress obtained by the method is more reasonable.
Claims (4)
1. A pile-supported reinforced embankment pile soil stress determination method is characterized by comprising the following steps:
(10) acquiring parameters: acquiring physical parameters of the pile-supported reinforced embankment, including pile length, pile distance, pile cap size, embankment filling height, the position of a reinforced body grid and external loading of the top surface of the embankment;
(20) and (3) calculating the additional pressure of the pile top: calculating pile top additional pressure according to the setting position of the reinforcement body based on the instability destruction mode of the reinforced embankment;
(30) and (3) calculating the pile top distributed load: calculating the pile top distributed load according to the pile top additional pressure and the pile top distributed load in the reinforcement-free embankment;
(40) calculating the soil reaction force between piles: and calculating the soil reaction force between piles according to the total load of the embankment and the load distributed on the pile top.
2. The pile-soil stress determination method of claim 1, wherein said (20) pile top additional pressure calculating step comprises:
(21) when the reinforcement body is arranged above the pile top by a certain distance u, the rigidity of the reinforcement body is higher, and the tensile modulus is more than 50GPa,
additional pressure of one layer of grid pile top:
adding pressure to the tops of more than two layers of n grid piles:
(22) when the reinforcement body is arranged above the pile top by a certain distance u, the rigidity of the reinforcement body is smaller, and the tensile modulus of the reinforcement body is not more than 50GPa,
the additional pressure of the pile top of the layer of reinforcement body is as follows:
adding pressure to more than two layers of n reinforced body pile tops:
wherein: t is the pulling force of the reinforcement body,
the vertical distance between the grid and the pile top is taken as the vertical distance;
the internal friction angle of the soil body;
for square caps, the cross-sectional area of the cap
，
The width of the cross section of the pile cap is a circular pile cap
，
The diameter of the pile cap;
the included angle between the broken surface and the horizontal plane, namely the included angle between the OA or O' A edge and the horizontal plane,
when the bottom surface of the foundation is completely rough,
is composed of
When the bottom surface of the foundation is completely smooth, the included angle is
，
The height of the filled soil of the embankment,ithe number of layers of the grid;
(23) when the reinforcement body is arranged at the pile top, the rigidity of the reinforcement body is higher, and the tensile modulus of the reinforcement body is greater than 50GPa, the pile top is subjected to additional pressure:
(24) when the reinforcement body is arranged at the pile top, the rigidity of the reinforcement body is smaller, and the tensile modulus of the reinforcement body is not more than 50GPa, the pile top is subjected to additional pressure:
wherein:
is a friction angle between the reinforcement body and the soil body,
is taken as the average value of
。
3. The pile-soil stress determination method according to claim 2, wherein the step (30) of calculating the pile top distribution load is specifically to calculate the pile top distribution load according to the following formula:
wherein:
the load is distributed on the pile top in the non-reinforced embankment and is obtained according to a related formula of the soil arch effect.
4. The pile-soil stress determination method according to claim 3, wherein the step of (40) calculating the inter-pile soil reaction force is specifically to calculate the inter-pile soil reaction force according to the following formula:
wherein:
is the counter force of soil between piles,
the weighted severity of the embankment fill is,
the height of the filled soil of the embankment,
the distance between the piles is set as the distance between the piles,
load is applied to the top surface of the embankment.
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| CN111241621B (en) * | 2020-01-13 | 2022-04-19 | 西南交通大学 | Stability evaluation method for high-strength pile composite foundation under embankment |
| CN113062161B (en) * | 2021-04-13 | 2022-11-01 | 金陵科技学院 | Pile top grouting pile-supported embankment and construction method thereof |
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